10W vs 10W-30 vs SAE 30 cylinder wear

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The SAE paper the following graph is from has been discussed in the aviation forum before. It shows the relative cylinder wall wear vs temp for straight 10W, 10w30, and straight 30.

Keeping in mind that this is just cylinder wall wear, I was still surprised that 10W and 10w30 didn't perform better at low temps. But the real surprise is just how flat the wear curve is for SAE 30.

Maybe the oils companies do know what they are talking about when they put something like the following in the PDS for straight grades: "Valvoline SAE 30, SAE 40, and SAE 50 offer excellent protection to gasoline engines operating under high temperature and heavy-duty service (hauling trailers, boats or RVs for sustained periods).

SAE082807.jpg
 
ok, so the real question here is... where is the bottom line on cold temp for straight 30 wt?

all the info you have been posting makes using valvoline SAE30 SM very tempting, but i still am not clear on how safe it is to low temps.

i live in toronto, canada. probably not good for me, right?
 
I wonder if they used a girly-man Energy Conserving 10w30. Bet a non-EC 10w30 like some high mileage versions, would have a flatter wear curve.
 
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Neat. Do you know when this test was conducted? I ask as it pertains to what API S_ designation these oils had.




Paper was presented in 1995 so the tests were done in 94/95, presumably. Oil used was API SG.

The focus on the test was determining the maximum OCIs for available oils at that time. The cold/hot cylinder wall test seems to have been done to approximate the wear encountered by law enforcement where you have a combination of start/stop low engine temp operation combined with occasional high speed, high stress operation. The authors of the study don't make any conclusions other than extreme temps at both the low and high end have a severe impact on cylinder and ring wear rates. They make no reference in the text as to any significance of the SAE 30 outperforming 10W and 10w30 at both temperature extremes.
 
Quote:


ok, so the real question here is... where is the bottom line on cold temp for straight 30 wt?

all the info you have been posting makes using valvoline SAE30 SM very tempting, but i still am not clear on how safe it is to low temps.

i live in toronto, canada. probably not good for me, right?




I think you'd be fine with SAE 30 from April to October. I think straight 30 would not be a good idea during the winter unless your car is in a heated garage at night, or you use a dipstick sump heater.

As a rule of thumb, for a modern (API SM) SAE 30 I think if winter temps in your area routinely drop into the lower 20F range (or lower) you need to use 10w30 or 5w30. If you only occasionally see temps in the lower 20F range, modern SAE 30 should be okay. If your winter temps rarely drop below 32F, modern SAE 30 is a viable year-round oil.
 
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G-MAN do you have any other tests of 30 weight?




I'm still researching. There seems to be a camp in the piston engine aviation community that prefers straight weight oils over multi-grades because of lower wear.
 
Can you mix 5w30 or 10w30 with a regular 30wt? if so wouldnt that be ok for the colder temps. like if you need 6 qts for your motor mix two qts of straight 30wt and 4 qts either a 5w or a 10w? just curious
 
has to do with HTHS and the fact that VII thickened oils DO NOT offer the anti scuff or film thickenes that a striaght grade will, IMHO a VII thickened oil acts only like the base vis oil BEFORE the VII is added in other words the 10/30 in this test acted like a striaght 10 wt would have IMHO maybe I'm wrong.
bruce
 
Schaeffers 7000 straight 30 (grp II+ & PAO) has some nice looking specs -

HTHS = 3.5
VI = 105
Pour pt(F) = -10
Evaporatoin = 5% (not sure if this is NOACK though).
TBN = 10

Could be an excellent seasonal oil here in Little Rock.
 
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What are they calling "10W"
confused.gif


10w is typically a 10w-20 and isn't rated for engines, per se~




No, a 20W is typically a 20w20. Valvoline makes a 10W that is SM rated. They may be the only company that does.

10W used to be a popular grade for those that used 30 or 40 in the summer and switched to 10W for the winter.
 
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has to do with HTHS and the fact that VII thickened oils DO NOT offer the anti scuff or film thickenes that a striaght grade will, IMHO a VII thickened oil acts only like the base vis oil BEFORE the VII is added in other words the 10/30 in this test acted like a striaght 10 wt would have IMHO maybe I'm wrong.
bruce




I think you are right. And I think what you've said points to why the RS4 with its fuel dilution issue shows such awful wear with VII laden 5w40 oils that meet VW's specs. Aromatic damage to the VI improvers only accentuates the oil's inability to cope with high temp/high shear situations, hence the increased wear.
 
Quote:


What are they calling "10W"
confused.gif


10w is typically a 10w-20 and isn't rated for engines, per se~




That was a new one for me too.

10W does exist as a single grade oil
http://www.burkeoil.com/pdf/sae10w1.pdf

The 1993 release of SAE J300 gives a min viscosity at 100C for 10W oil. It's thinner than a 20 weight. It looks like it could be called a 10W-10 if there was an SAE 10 in J300.

Here's bunch more from the horses mouth
http://eolcs.api.org/FindBrandByViscosity.asp?Viscosity=10W

How about single grade 5W oils? there aren;t any listed, but API has a placeholder here:
http://eolcs.api.org/DisplayInfo.asp?Info=Viscosities

Could just as well have a single grade 0W, woops, they do....
http://eolcs.api.org/FindBrandByViscosity.asp?Viscosity=0W
 
Diesels generally spec thicker oils than gas engines.
I would like to add this graph's info [concerning one diesel engine's rings/bore wear] to more wear data from other parts of an modern gas engine.
Right now, it seems to be a partial and isolated picture to me.
 
JAG posted a series of charts a while back that showed oils with VII did poorly compared to oils without in terms of film strength. This seems to be a supporting graphic to those, and goes along with what Bruce said.
 
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